updated the CHANGELOG and __pkginfo__.py files

CHANGELOG

+version 1.0.4.rc1
+----------------
+* bug fix in IWidget: the label of the configurator was not taken into account
+* bug fix path_to_module function: the list of directories has to be parsed backwards
+* raise an error when none or more than atom matches the mass stored in the LAMMPS config file
+* modified the label for r value
+
 version 1.0.3.e:
 ----------------
 * bug fix relative to REGISTRY update

MDANSE/__pkginfo__.py

-__version__ = "1.0.3.e"
+__version__ = "1.0.4.rc1"
 
-__date__ = "18-11-2016"
+__date__ = "22-11-2016"
 
 __author__ = "Eric Pellegrini"